Renogy Pro S1 120Ah Battery Beta Test Report (Week 2) - Cold Weather T | Renogy US

This report covers the critical cold-weather performance testing conducted on November 10, 2025.

Test Environment: Outdoor, snowy conditions. Ambient temperature was 1°C, feels like -4°C.
Test Objectives:

Validate the self-heating function when charging in below-freezing conditions.
Validate the battery's ability to discharge high amps while cold.
Perform a deep discharge test to find the 0% SoC shutdown point and observe voltage performance under load.

Test 1: Self-Heating (Cold Charge) Data Log

Objective: To validate the self-heating function. The battery was at a "cold soak" state.

Time	SoC %	Volts (V)	Amps (A)	Temp (°C)	Heater Status	Warnings/User Notes
15:23	65.4%	13.3V	0A	1.1°C	Off	"Charge Low Temp Protection" Active
15:26	65.4%	13.1V	-8.9A	1.1°C	Off	(Small load from trailer systems)
15:27	65.3%	13.74V	+35.5A	1.1°C	ON	TEST START: Shore power applied. Heater turned ON instantly.
15:39	71.1%	13.89V	+34.4A	5.2°C	ON	SUCCESS: Battery is warming up while charging.

Analysis: The self-heating function worked perfectly. The moment a charge was applied to the 1.1°C battery, the BMS correctly diverted power to the 85W heater and began raising the battery's internal temperature, allowing it to safely accept a charge. The test was stopped at 5.2°C, but it is clear the heater was functioning as specified (it is expected to turn off >10°C).

Test 2: Deep Discharge (Cold) Data Log

Objective: To test the battery's performance under a high load from a cold state down to 0% SoC. Load: 950W Parabolic Heater (~92-100A draw).

Time	SoC %	Volts (V)	Amps (A)	Temp (°C)	Heater Status	Warnings/User Notes
15:49	74.6%	12.82V	-92.0A	9.2°C	Off	TEST START: Charge disconnected, heater ON.
16:20	35.59%	---	-96.1A	---	Off	---
16:--	33.5%	12.86V	-10.0A	19.3°C	Off	(Heater off. Note: "LED, TV+Firestick, 12.86V stable")
16:26	31.5%	12.2V	-94.6A	19.5°C	Off	CRITICAL FINDING: "Voltage drop to 12.19 causes electronics to turn off (TV+Firestick)"
16:27	29.7%	12.2V	-94.6A	20.0°C	Off	Note: "12V TV will NOT turn on." "Remaining Time" estimate of 24m seems accurate.
16:29	27.7%	12.09V	-94.9A	20.6°C	Off	"Battery Undervoltage Warning" Active.
16:31	25.2%	11.97V	-96.1A	21.4°C	Off	Undervoltage warnings continue.
16:35	20.2%	11.78V	-96.6A	23.3°C	Off	---
16:37	16.7%	11.76V	-97.4A	24.8°C	Off	Note: "Remaining Time" now shows 2h 12m (Highly inaccurate).
16:43	9.7%	11.23V	-100.5A	28.3°C	Off	Cells: 2.82, 2.82, 2.81, 2.80
16:44	7.7%	10.98V	-101.9A	29.3°C	Off	Note: "KS2 inverter alarm because voltage dropped too low"
16:45	0%	11.24V	0A	30.2°C	Off	CRITICAL FINDING: BMS SHUTDOWN. (Last screenshot at 7.7% / 10.98V before final shutdown).
16:46	0%	12.38V	0A	30.4°C	Off	(Load removed, voltage rebounding)

Test 3: Recovery from Deep Discharge

Time	SoC %	Volts (V)	Amps (A)	Temp (°C)	Heater Status	Warnings/User Notes
17:05	0.1%	12.97V	+42.5A	27.1°C	Off	CRITICAL FINDING: "Battery was fully 0% and not even Bluetooth worked. Now charging..."
17:17	7.09%	---	+44.0A	---	Off	---
17:46	23.8%	13.43V	+44.1A	21.9°C	Off	---
17:50	24.2%	13.27V	0A	21.2°C	Off	(Charge stopped to prep for next cold soak)

Week 2 Key Findings & Analysis

Critical Finding: Significant Voltage Sag Under Load. The most significant finding from this test is the battery's voltage performance under a standard, high-amp load. At a 31.5% SoC, a single 94.6A load (one 950W heater) caused the battery's voltage to drop from a stable 12.8V (at -10A) to 12.2V. This drop was severe enough to shut down other 12V-dependent electronics, including the trailer's TV and Firestick. This is a disappointing result, as one would expect the battery to maintain a more usable voltage (above 12.5V) while under a load that is well within its 150A continuous rating.
Self-Heating Works Perfectly: The test at 15:27 provides 100% confirmation that the self-heating function operates as designed, turning on automatically when a charge is applied in sub-freezing temperatures.
BMS Shutdown Sequence is Robust: The battery correctly protected itself at the end of the discharge test. The log shows a clear, safe shutdown sequence: 1) At 16:29 (27.7% SoC), "Battery Undervoltage" warnings appeared. 2) At 16:44 (7.7% SoC), the voltage dropped to 10.98V, triggering the inverter's low-voltage alarm. 3) At 16:45, the BMS performed a final, protective shutdown of the battery.

Deep Discharge "Blackout": The finding at 17:05 that the battery's Bluetooth also shut down is critical. This means a user who fully depletes this battery cannot check its status and must apply a charge to "wake" the BMS. This is important information for any user.
App "Remaining Time" is Unreliable: The "Remaining Time" calculation is a significant software flaw. It jumped from an accurate "24m" (at 16:27) to a wildly inaccurate "2h 12m" (at 16:37) while under an even higher load. This is misleading and should be reported to the app development team.

Graphing Analysis

Charge Rate (with internal Heater): From 15:27 to 15:39 (12 minutes), the battery gained 5.8% SoC (65.3% to 71.1%). This is a rate of 0.48% per minute while the 85W battery self-heater was also on.
Discharge Rate: From 15:49 to 16:45 (56 minutes), the battery drained 74.6% SoC(74.6% to 0%). This is a rate of -1.33% per minute under an average load of ~95A.
Temperature Rise (Load): During the 56-minute discharge test, the battery's internal temperature rose from 9.2°C to 30.2°C (a 21°C increase) just from the internal resistance of discharging.
Temperature Rise (Heater): During the 12-minute charge test, the battery's temperature rose from 1.1°C to 5.2°C (a 4.1°C increase) from the heater alone.

Week 2 Conclusion

This week's test successfully validated the battery's advanced cold-weather features. The self-heating function works perfectly. However, the deep discharge test revealed a significant real-world limitation: severe voltage sag.

The battery cannot maintain a stable 12V+ output for other electronics when under a high (but rated) load, causing system-wide issues. This, combined with the buggy "Remaining Time" in the app, are the two most critical pieces of feedback for this test cycle.